Time： 2019-02-26 15:14:45
Author： Shenzhen Yanbixin
How to distinguish high quality filters？
The purpose of the line filter is to suppress electromagnetic noise. The function is to obtain a power signal of a specific frequency by inserting a power filter into the power line, or to eliminate a power signal after a specific frequency. When using, we need to understand the knowledge of the power filter, so as to prevent unnecessary losses, and we need to know how to choose the power filter when using, as follows:
1: insertion loss
(1) Insertion loss definition Insertion loss is one of the most important technical parameters of EMI power filter. The central problem considered by designers and engineering application personnel is to ensure that the filter safety, environment, machinery and reliability can meet the requirements of relevant standards. Under the premise, achieve the highest possible insertion loss.
(2) Common mode loss and differential mode loss The insertion loss of the EMI power supply filter includes common mode (expressed as CM) insertion loss and differential mode (expressed as DM) insertion loss.
(3) Factors affecting the insertion loss factors affecting the insertion loss of the power EMI filter include impedance matching and installation.
2: Impedance matching
(1) Reasons for impedance matching When selecting a filter, first select the filter circuit and insertion loss performance that are appropriate for your application.
(2) Impedance mismatch analysis In order to achieve better filtering effect, according to the filter mismatch principle: if the actual load is inductive high resistance, select the output load as a capacitive low resistance filter; if the actual load is capacitive For low resistance, select the output load as an inductive high-impedance filter. Similarly, for the input impedance of the filter and the source impedance of the grid, the filter should also be selected according to the principle of impedance mismatch.
3: rated voltage
The rated voltage is the operating voltage at which the power EMI filter is used at the specified supply frequency and is also the maximum allowable voltage value of the filter. For a filter with a single-phase power supply, the rated voltage is 250V; for a filter with a three-phase power supply, the rated voltage is 440V. If the voltage of the input filter is too high, the internal capacitor will be damaged;
4: rated current
Rated current: The maximum continuous operating current allowed at rated voltage and specified ambient temperature.
We should choose the rated current of the filter based on the actual maximum operating current and operating ambient temperature.
From the above we know that we must know the rated voltage, rated current, insertion loss and other related aspects at the time of purchase. Today's electronic products are aimed at miniaturization, high performance, high precision, high reliability, and high reactivity. The distribution density of circuit components is too high, and the size of the circuit is greatly reduced. However, the circuit is more compact. More components will be squeezed into a small space, increasing the chance of interference, with electromagnetic interference and noise being the most disturbing. The emergence of a power filter solves this problem.